Recently, as the integration degree and the precision of semiconductor devices increase, the formation of ultra-fine photoresist patterns, which have a half pitch of less than 90 nm, is required in the photolithography process for producing the semiconductor devices. Thus, in the photolithography process, the wavelength of an exposure light is reduced to less than 193 nm, and various technologies for optimizing the pattern forming process have been being developed. In order to produce the fine photoresist patterns, it is also necessary to develop photosensitive materials having a low LER (Line Edge Roughness), a low PEB (Post Exposure Baking) temperature sensitivity, and a good dry etching resistance.
In order to improve the resolution and the process margin in forming the photoresist pattern, and to produce a more fine photoresist pattern, the photosensitive photoresist polymer should have a low activation energy in the deprotection reaction of a protecting group, in which the protecting group is adhered to the side chain of the photoresist polymer for inhibiting the dissolution of the polymer against a basic solution. Preferably, the photosensitive polymer should be materials having a low PEB(Post Exposure Baking) temperature sensitivity, that is, materials which are less affected by an acid. In summary, a fine photoresist pattern can be obtained by using a polymer which is less affected by an acid and whose main chain is decomposed by the light exposure.